PSI - Issue 17

Pedro J. Sousa et al. / Procedia Structural Integrity 17 (2019) 828–834 Sousa et. al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 6. Mechanical design of the developed system

In order to simplify the manufacturing procedure, the parabolic mirror was divided in two parts to provide easier access to its interior and thus facilitate the polishing process. The multiple external supports of the system were closely aligned with the center of mass of the whole system, also including the electronics. The LED can generate significant amounts of heat if operated continuously. In order to ensure proper heat dissipation, a heatsink with a 100 mm fan was also included in the assembly. For applications with sufficient time between pulses, cooling is not essential, however, it comprises a useful safety feature. Furthermore, it also increases the versatility of the designed system, allowing its use with higher duty cycles. This article reports the development of a dedicated illumination system for use with high-speed digital image correlation. Its behavior was simulated and tested in order to ensure the required response times as well as to understand its performance. First, the electronic power control circuit, that is capable of outputting light pulses of hundredths of nanoseconds, was analyzed and various factors that significantly influence its performance were recognized. For example, the limiting resistor (R1) was found to have significant influence, as it limits the maximum pulse rate, startup time and number of systems that can be used in parallel. Afterwards, simulation was used to design the optical reflector: a parabolic mirror with 9 mm focus distance and 165 mm diameter, which produced a beam diameter of approximately 250 mm at a distance of 1 meter. Finally, a mechanical system comprising all these parts was designed with concerns regarding total weight, weight distribution, cooling, manufacturability and versatility. The developed system is a specialized tool for high-speed digital image correlation applications, with reduced heat buildup in the specimen and lower power usage than continuous illumination systems. 5. Conclusions

Acknowledgements

The authors gratefully acknowledge the funding of Project NORTE-01-0145-FEDER-000022 - SciTech - Science and Technology for Competitive and Sustainable Industries, co-financed by Programa Operacional Regional do Norte (NORTE2020) through Fundo Europeu de Desenvolvimento Regional (FEDER). Pedro J. Sousa gratefully acknowledges the FCT ("Fundação para a Ciência e a Tecnologia") for the funding of the PhD scholarship SFRH/BD/129398/2017.